Alexander Marakovits, spokesperson for the Interior Ministry, told The Salzburger News, "We also have this information and have checked it, but cannot say with absolute certainty that it is true. But the parents have been informed their daughter could be dead."

Konrad Kogler, Director General for Public Security, also confirmed there were unverified rumours on Sunday evening's ORF program 'In the Centre'.

The motivations of the two Bosnian born girls, aged 15 and 16, are unclear. Before leaving, they had contact with Chechen youths, and visited a mosque in Vienna's second district.

Photo: Interpol

After their departure via Turkey, the teenagers regularly posted status updates on social media from Syria. Interpol has been searching for the girls since April.